Spark plug



Aug. 4, 1925'. f 1,54s,o31-

n f E. T. FRANZEN 4 SPARK PLUG l Filed March 5, 1923 y INVENTOR' ATTORNE Y Patented Aug. 4, 1925.

UNITED 'STATES ERIC T. FRA-NZEN, on MAPLEWQOD, NEW JERSEY.

SPARK I'LUG.

Application mea March 5, 1923. serial No.. 622,768.

To all whom t may concern.' Y

Be it known that` I, ERIC T. FRANZEN, a citizen of the United States ofAmerica, residing at Maplewood, in the county of Essex and State of NewJersey, have invented new and useful Improvements in -Spark Plugs, ofwhich the following is a specilication.

This invention relates to improvements in spark plugs as usednconnection with internal combustion engines and has as one of itsobjects to providea-spark plug having a spark gap automaticallycontrolledby the heat engendered by explosion vof the gases within theengine cylinder. i A

Another purpose lis to produce a spark plug in which the gap is closedinitially due to the relativeV coldk condition ofthe parts and which',becoming heated during operation, causes the gap to open variablyaccording to the temperature ofthe plug and'its associated elements.

A further aim is the provision of a spark plug so designed as to enable.the user to ascertain whether or not the cylinder lin which theplug isused is properly firing, by observation of the variable spark gap,thereby providing a visual means for detecting missing cylinders ofinternal combustion engines. 1

These several objects are attained by certain structural arrangements inthe outer portion of the plug body andconstruction of parts therein, ashereinafter rdescribed and illustrated Vin vthe annexed drawing, formingpart hereof, and in which y Y Figure 1 is a side view of a conventionaltype of spark plug, its upper portion being in section to show theapplication of an embodiment' of the invention.

FigureI 2 is a transversesectional view taken on line 2 2 of Fig. 1.

Figure 3 is a perspective view showing one form of thermostatic coupleas usedin the device and drawn to an enlarged scale.

Figure l is a fragmentary sectional View illustrating the application ofa modified form o'f the same.

As will be readily recognized in the drawing a conventional spark plugis shown having a body 10' terminating in a reduced screw-threadedportion 11 and containing an insulator 12 held by the clamp nut 13.

A fixed electrode 14 extends below the threaded base 11 and containedcentrally in the insulator is the mating'electrode 15.

The-upper portion of the insulator 12 contains Va circular recess orchamber 16 open at lits outer end which is internally screwthreaded toreceive a bushing 17 having an extending liange 18. i

Disposed in the recess 16 is a relatively thin sleeve' 19 made ofnon-conducting, transparent material, as mica, the same covering 'theinnerVV ends of transverse openings 2.0 formed through the insulator.

- Into this recess, concentric with thesleeve 19, 'extends'the upper endof thev electrode 15, v`terminating within the range of the sightopenings '20. i

Threadedinto the bushing 17 is a metal plug 21 provided 'witha washer 22resting on the flange 18 and abovethe washer a clamp nut 2311s threadedon the stud 21.

f A thermostatic' element, generally desiglnatedbythe ,numerall 25adapted to operateV by changes in temperature, (best shown in detail inFig. 3) is composed of two metallicplates, 24 and 26, having dilferentratios of expansion` when subjected to heat,

assteel land brass, is coiled at one end to produce a neck 27, the samebeing tight l' fitted intoy a hole eccentrically formed in the inner endof the plug 21. e

These plates are permanently and fixedly united over theirentirefcontacting surfaces and are so bent as to present the brasssurface into position. to make positive electric contact with theadjacent end of the electrode 15.

In the modification shown in F ig.4.-`the bushing is formed with abottom wall 17 and has an opening at one side through whichthethermostatic couple .is entered and bent at a. right angle, the samebeing held rigid by the inner end of the stud 21, the device being inall other respects as previouslydescribed and operates in the samemanner.

In starting a cold engine the sparking current will be conveyed from aconductor clamped between the nut 23 and washer 22, to the stud 21 andthence through the thermostatic couple 25 to the electrode 15 direct.

As theengine and its associated parts become heated, the inner ory brassplate 26 f Y delivered spark in a well known manner.

constituting a The spark passing the gap is readily observable throughthe `openings 20 but entrance of dust, oil, gases and the like areprevented, due to the transparent sleeve 19 enclosing the recess inwhich the spark gap is confined, and it 'is to be noted that all theseveral parts are enclose-d within the body of the spark plug, nounsightly pr0 jections or excrescencies being used.

Cbviously when these plugs are in use in a. multi-cylinder engine, theuser may, by o'bserving the distances between the couple 25 and theelectrode 15 determine the conditions within the cylinders.

@wing to the high temperature attained bythe succession of explosionswithin the cylinders, it will be understood that the gaps between theelectrodes 15 and the couple 25 will, under proper conditions, remain attheir maximum, but should any cylinder miss tiring for any appreciablelength of time, the gap in its plug will materially shorten so that theuser may determine almost instantaneously, the condition.y

Although the foregoing is descriptive of the preferred embodiment or theinvention, it will be apparent that minor changes may be made in itsconstruction, without the exercise of invention or conflicting with thescope ot' the claims hereto appended.

Having thus described my invention, what I claim as new and desire tosecure by Letters Patent, is

1. A spark plug having an insulated electrode, a thermostatic couplevforming part oi said electrode, said couple being pendantly supportednormally in contact with the electrode and in the circuit leadingthereto, said couple being wholly enclosed within the outer portion ofthe insulator and having its terminal visible through openings in theinsulator.

2. A spark plug comprising a body having an electrode, an insulatorsecured in said body, said insulator having a recess in its upperportion, a second electrode carried by said insulator. and projectinginto the recess, a terminal plug ixed in the outer end of saidinsulator, and a thermostatic couple carried by said plug adapted todirectly con- Vvey current to said electrode within the recess orpresent a gap therebetween.

3. A spark plug comprising abody having a fixed electrode, an insulatorcarried by said body, said insulator having an open axial recess in itsouter end, a second electrode extending into the mentioned recess, abushing fixed in the outer end of the recess, a terminal plug in saidbushing, and a thermal unit fixed in said plug extending into the recessadjacent said second electrode and adapted to convey current thereto,said unit being automatically movable to or from the electrode.

1. A spark plug comprising a body having a lixed electrode, an insulatorcarried by said body, said insulator having an open axial recess in itsouter end and transverse openings intersecting the recess, a transparentsleeve tting the recess, a terminal fixed on the end ot' said insulatorover the recess, and a thermal unit attached eccentrica-lly to saidterminal adapted to convey current to said second electrode either vbydirect contact or through a gap therebetween in accordance with thetemperature of said parts. Y

5. 1n a spark plug having an outwardly extending insulator, saidinsulator containing an axial chamber in its outer portion, anelect-rode having a part entering the chamber, said insulator havingtransverse openings intersecting the chamber in the plane of theelectrode end, a. transparent sleeve in said chamber covering the innerends of the mentioned openings, a bushing threaded into the open end otthe chamber, a terminal plug in said bushing and a thermal couple fixedin said plug and movable in the chamber to convey current to saidelectrode.

This speciication signed and witnessed this 19th day of February, 1923.Y

ERIC T. FRrrllZEN` lVitnesses F. NOLL, FnnDK. C. FISCHER.

